1. Field of the Invention
The invention relates to methods and systems for esterification and transesterification of fats and oils.
2. Description of the Related Art
Fats and oils consist mainly of triglycerides and free fatty acids in various proportions. Subjecting these fats and oils to esterification and/or transesterification reactions yield a mixture of esters and glycerol as the primary reaction products. The esters produced can be used as a biodiesel fuel or as components in other useful industrial and consumer products.
Many procedures currently used to convert fats and oils to esters involve mixing the fats or oils with an alcohol (such as methanol), miscible catalysts, and sometimes a co-solvent. The use of a co-solvent promotes the formation of single phase, preventing the separation of the alcohol and the fats or oils. Typically, an acidic miscible homogenous catalyst such as sulphuric acid dissolved in the alcohol is used to esterify free fatty acids, while a basic miscible homogenous catalyst such as sodium hydroxide or potassium hydroxide is used the transesterify the triglycerides. These catalysts are typically applied sequentially in a two-stage process. Heterogeneous catalysts have also been used for esterification and transesterification reactions using an oil/fat and an alcohol, but the oil and alcohol phase separation that occurs significantly impedes the reaction rate, thus resulting in long residence times lasting up to several hours and poor product yield.